The size of implementation in integrated circuits can significantly affect the cost of manufacture. One of the key design blocks in integrated circuits is the inductor, which are often considered an area-consuming component due to the inductor's planar shape. Therefore, the number of inductors included with an integrated circuit should be minimized in order to reduce the overall size of the integrated circuit.
FIG. 1 illustrates an implementation of a large power amplifier 101. In particular, the large power amplifier is implemented using multiple power amplifiers 102, 103, 104 in which the respective inputs and outputs are directly connected to each other. The interconnections of the inputs of power amplifiers 102, 103, 104 result in large parasitic elements 105, 106, 109, 110, 113, and 114 being present at the inputs, thereby resulting in uneven driving of the power amplifiers 102, 103, 104. Likewise, parasitic elements 107, 108, 111, 112, 115, 116 would also be present at the outputs of power amplifiers 102, 103, 104.
Parallel amplification power amplifiers have been utilized to attempt to overcome one or more of the deficiencies described with respect to FIG. 1. In the design of power amplifiers in parallel amplification in CMOS technologies, each power amplification path requires inductive interstage matching between the corresponding driver and the power stages due to each CMOS devices' capacitive input characteristics. Thus, the number of inductive interstage matching components increases in accordance with a similar increase in the number of parallel amplifications paths. Having a large number of interstage matching inductors would consume a large area, thereby increasing the cost of implementation.
As an example, FIG. 2A illustrates a conventional power amplifier system that includes multiple power amplifiers 207, 208, 209 and an output matching network 210. Cascode amplifications for high gain require driver amplifiers 201, 202, 203 in which their respective outputs need to be matched to the respective inputs of power amplifier amplifiers 207, 208, 209. In CMOS designs, the matching is typically performed by inductive components due to the capacitive nature of CMOS devices. These inductive components can be inductors 204, 205, and 206. It will be appreciated that the use of multiple respective inductors 204, 205, 206 for matching can consume significant area in an implementation of an integrated circuit.
FIG. 2B illustrates another conventional power amplifier system similar to that of FIG. 2B. In particular, there are multiple power amplifier driver amplifiers 211, 212, 213, and a corresponding number of power amplifiers 217, 218, 219. Likewise, there is an output matching network 220. However, the matching between the respective outputs of driver amplifiers 211, 212, 213 and respective inputs of power amplifiers 217, 218, 219 is based upon respective transformers 214, 215, 216. It will be appreciated that the use of multiple respective transformers 214, 215, 216 for matching can consume significant area in an implementation of an integrated circuit.
Therefore, there is a need in the industry for the sharing of inductor interstage matching in a parallel amplification system.